Absorptive devices often comprise articles of manufacture designed to receive and retain bodily fluid discharges, with diapers, sanitary pads, bed pads, incontinence pads, towels, bandages and the like being well known. Disposable absorbent devices are designed to be used once and discarded, enhancing both convenience and hygiene.
Generally, known disposable absorptive devices comprise an absorbent core covered on one side with a topsheet which preferably contacts the body, and covered on the distal side with a fluid-impermeable backsheet. The backsheet prevents absorbed (bodily) fluids from leaking out of the device and soiling the wearer, clothing or bedding. Polymer film apertured topsheets, known in the art, are generally made of hydrophobic material (e.g., polyethylene) which is impervious or impermeable to liquids. A primary reason that fluid often remains in contact with the wearer's body is that hydrophobic polymer films, by their very nature, do not absorb moisture. Another disadvantage of conventional devices is discomfort due to the hot, sweaty, and sticky feel on the wearer's skin often associated with products including hydrophobic polymer film. This discomfort, for example, may be due to extended contact between fluid and the wearer's skin in normal use of products of this nature.
Accordingly, these products have had inherent and sometimes severe negative characteristics and less than favorable acceptance by some consumers.
In attempting to overcome the disadvantages of hydrophobic polymer film topsheets, devices have been designed to exhibit greater surface dryness. Hydrophobic polymer film topsheets have been created with openings or tapered capillaries for channeling fluid through the topsheet into the absorbent core in discrete points, so that the amount of fluid left on the wearer's skin is hopefully reduced. Tapered capillaries also have been designed to prevent "rewetting", which is reverse flow (reflow) of fluid from the absorptive core back through the topsheet and onto the skin. Rewetting can be caused by common bunching or compression of the product often encountered in normal use of absorptive devices. The tapered capillaries generally include excess material against the absorbent core that is designed to block the capillary in the reflow direction, however, are inefficient because each drop of liquid must contact a capillary in order for it to travel through the capillary into the absorbent core. Consequently, there remains prolonged exposure of fluids to the wearer's skin. In addition, the amount, size and placement of the capillaries is critical for reducing the amount of fluid contacting the wearer as well as the wearer's length of exposure to the fluid. While location and structural characteristics of such capillaries can be optimally designed in theory, maintaining these critical parameters in use has been consistently unreliable in existing products.
In order to address these inefficiencies associated with hydrophobic polymer film topsheets, surfactants have sometimes been added to improve fluid flow through the topsheet. Surfactants modify the surface of an hydrophobic film topsheet to render it hydrophilic, i.e. to confer wettability, so that fluid more quickly passes through the topsheet to the absorbent core at discrete points. Wettability is the spreading of a fluid on a surface due to reduced surface tension of such flow and/or surface energy of the surface. However, the use of surfactant compromises the device's overall fluid handling ability when the surfactant is desorbed by bodily fluids. Fluids that pass through a topsheet having surfactant disposed thereon acquire some of the surfactant, which reduces the surface tension of the fluid and, in turn, compromises the effective absorbent properties of the absorbent core. Also, aging of the surfactant reduces its effectiveness at rendering the topsheet wettable, thereby reducing the effective "shelf-life" of any product including surfactant treatment. Surfactant also can be rubbed off the surface during handling and packaging. Another disadvantage to using surfactant is the increase in cost of production as well as possible allergic reactions and skin irritations.
Another attempt to overcome problems associated with the prior art devices is the use of hydrophilic material, usually in the form of a foamed sheet which is produced from hydrophilic groups and epoxy resins. However, a disadvantage associated with foamed sheets is their lack of utility as a formed film topsheet.